Continuation of a far-reaching investigation concerned with the isolation, characterization and structural elucidation of new and potentially useful cancer chemotherapeutic agents from marine animals and to a lesser extent from plants and terrestrial arthropods has been outlined. Renewal support would be used exclusively to isolate and characterize anticancer agents from the confirmed active extracts of 22 marine invertebrates, 11 marine vertebrates, 6 terrestrial arthropods and 4 plants. Maximum effort on the renewal program will be devoted to the marine animal species affording extracts with outstanding confirmed level activity (T/C greater than 150) in the National Cancer Institute's murine PS lymphocytic leukemia screening system. As each of these problems is solved (or placed in a lower priority due to decreasing or lost activity during fractionation guided by bioassay) it will be replaced by another of high priority from a current pool of some 300 marine animal species giving extracts with confirmed level activity. The lower animals represent a virtually untapped but potentially very fruitful source of new antineoplastic agents and every effort will be directed at making such new substances available to the Division of Cancer Treatment, National Cancer Institute.